Trypanosoma brucei, a WHO category one pathogen (emerging and uncontrolled), causes human African trypanosomiasis (HAT, aka African Sleeping Sickness), which is invariably fatal unless treated. New drugs are badly needed since current therapy is limited by toxicity, difficulty of administration, and spreading drug resistance. A wealth of knowledge has accumulated over the last 20-30 years on the molecular and cellular biology of T. brucei through a variety of hypothesis driven research programs. While several validated drug targets have arisen as a spin-off of these studies, there has been no systematic comprehensive effort to exploit the output of the genome projects and the recent advances in genetic manipulation of T. brucei to specifically identify and assess potential of drug targets. In addition, significant resources have been invested in setting up drug discovery programs including the building of facilities for high throughput screening (HTS) in several academic centers around the world. However, despite these efforts the list of validated drug targets that are both essential and likely to be "druggable" is small, and thus there are not enough high value targets that justify the considerable effort and resource of a HTS, or a dedicated drug discovery effort. This proposal is part of a coordinated effort by our US-based group (Stuart and Phillips) and our collaborators in the UK (Drs. M. Fergusson and J. Mottram), to undertake RNAi (interfering RNA) analysis in a genome-wide survey for essential, and "druggable" targets in T. brucei. A genome-wide data-base that lists key data required for target assessment in drug discovery is being compiled by the WHO/TDR and will be a key resource for target selection. While this proposal focuses on HAT, genetically validated targets in T. brucei may translate to T. cruzi and Leishmania species, and thus these studies will provide a resource for the entire kinetoplastid community. All data generated from the project will be provided to the tdrtargets.org curators for public distribution on that web site. The goals of this three year study are to 1) Select 200 - 300 genes in the T. brucei genome for RNAi essentiality analysis based on an assessment of potential "druggability";2) to determine if the selected genes are essential for the growth of blood form T. brucei parasites in vitro and in vivo by RNAi analysis;3) to develop high-yield heterologous protein expression systems and suitable enzyme assays for genes that are shown to be essential;and 4) to organize data and reagents to provide distribution to the T. brucei research community. PUBLIC HEALTH RELEVANCE: The goal of the National Institute of Allergy and Infectious Diseases (NIAID) is to support basic and applied research leading to a better understanding of infectious, immunologic, and allergic diseases with the goal of generating new treatments or prevention programs for these diseases. The direct goal of this proposal is to identify new drug targets for the development of novel treatment programs against several priority trypanosomal pathogens that have been of long standing interest in the NIAID portfolio.